Well....It's not just the families who might feel a bit inconvenienced.
Last year, I had to fly back from Luanda to CDG in Economy because the Business Section was full, and I found myself sitting next to two youngish children ( maybe 10 or 11 years old ) who were seperate, didn't know each other, one in the middle seat, one in the window seat.
I spent the whole nine hours or so being interrupted either by the children wanting to get past to go see their parents for something, or the parents leaning over me to talk to the children.
Felt like quite probably the longest, worst flight of my life.